\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1.5]
  % \useasboundingbox(-1,-2)rectangle(8,6);
  \tkzSetUpPoint[fill=black]
  \tkzDefPoints{0/0/O,-0.5/-0.5/A,1/0.8/B,-1.5/0.9/C}
  \tkzDefPointOnLine[pos=3.0](O,A)\tkzGetPoint{A'}
  \tkzDefPointOnLine[pos=1.8](O,B)\tkzGetPoint{B'}
  \tkzDefPointOnLine[pos=1.4](O,C)\tkzGetPoint{C'}
  \tkzDrawPoints(O,A,B,C)
  \tkzLabelPoints(A,B,C)
  \tkzLabelPoint[below right](O){$+Q$}
  \draw[thick,->](A)--(A')node[left]{$F_A$};
  \draw[thick,->](B)--(B')node[above]{$F_B$};
  \draw[thick,->](C)--(C')node[left]{$F_C$};
  \draw[thin,densely dashed](O)--(A)node[midway,above]{$r_1$};
  \draw[thin,densely dashed](O)--(B)node[midway,above]{$r_2$};
  \draw[thin,densely dashed](O)--(C)node[midway,above]{$r_3$};
\end{tikzpicture}
\end{document}